Free Landscape Calculator

Fertilizer Calculator

Calculate exactly how many pounds and bags of fertilizer you need based on lawn size, fertilizer type and nitrogen application rate. Instant results with cost estimates.

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Fertilizer Calculator
Bags and pounds needed for your lawn
Lawn Dimensions
ft
ft
📐 Your Results
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Pounds
Fertilizer needed
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Bags
Bags to buy
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Square Feet
Lawn area
Estimated Cost
Avg. $25–$45/bag
$—
💡 Always order 10–15% extra for waste and settling.

📊 Understanding Your Results

Pounds of Fertilizer — Total weight of fertilizer product needed to deliver the target nitrogen rate to your lawn area.

Bags to Buy — Number of bags needed rounded up. Store leftover fertilizer in a cool, dry location.

Cost Estimate — Based on average US fertilizer prices of $25–$45 per bag.

How the Fertilizer Calculator Works

Our fertilizer calculator uses the nitrogen content (first number in NPK) and your target nitrogen application rate to determine exactly how much product to apply.

The Fertilizer Formula

Step 1: Lawn Area (sq ft) = Length × Width
Step 2: Fertilizer (lbs) = (Area ÷ 1,000) × N Rate × (100 ÷ N%)
Step 3: Bags = Fertilizer lbs ÷ Bag size (round up)
Step 4: Never exceed 1 lb of nitrogen per 1,000 sq ft per application

Example: 5,000 sq ft, 10-10-10, 1 lb N rate = (5 × 1) × (100÷10) = 50 lbs = 1 bag of 50lb fertilizer. Cost = $35.

Fertilizer NPK Guide

FertilizerN-P-KBest ForRate
All-Purpose 10-10-10Equal NPKNew lawns10 lbs/1,000 sqft
Slow Release 24-0-11High NEstablished lawns4 lbs/1,000 sqft
Scotts Turf Builder30-0-4Lawn greening3.3 lbs/1,000 sqft

Frequently Asked Questions

Common questions about lawn fertilization and NPK ratios.

How much fertilizer per 1,000 square feet?
At 1 lb N rate: 10-10-10: 10 lbs, 24-0-11: 4.2 lbs, 30-0-4: 3.3 lbs per 1,000 sq ft. Always check the bag label for manufacturer’s recommended settings.
How often should I fertilize my lawn?
Cool-season grasses: 2–4 times per year, mainly in fall. Warm-season grasses: 3–5 times during the growing season May–September.
What does NPK mean on fertilizer bags?
N = Nitrogen (green leaf growth), P = Phosphorus (root development), K = Potassium (stress resistance). A 10-10-10 bag contains 10% of each by weight.
Can I over-fertilize my lawn?
Yes — over-fertilizing causes fertilizer burn. Never exceed 1 lb of nitrogen per 1,000 sq ft per application. When in doubt, apply less and fertilize again in 6–8 weeks.
Should I fertilize before or after rain?
Apply before light rain (0.25–0.5 inches) for ideal activation. Never apply before heavy rain over 1 inch — fertilizer washes into storm drains. Water in if no rain expected within 48 hours.

💡 Fertilizer Schedule

Spring: Light feeding — starter or balanced

Summer: Slow release only

Early Fall: Heavy feeding — high nitrogen

Late Fall: Winterizer — high potassium

Winter: No fertilizer